CURIOUS INHABITANTS OF THE GULF STREAM 
173 
Red Snapper, which is taken in com¬ 
paratively deep water, being perhaps the 
most important commercially. 
The excellence of the Red Snapper is 
widely known, and quantities of this fish 
are shipped to distant northern markets. 
For baking, a fine large one has few 
equals. Bright red color in fishes has 
often a peculiar significance, which will 
be spoken of later. 
Though not exactly a snapper, the ex¬ 
cellent table-fish known as the Yellow 
Tail (Color Plate, page i8i) belongs to 
the snapper family. It is somewhat more 
elongated than the true snappers, with 
lines more graceful, and its tail-fin is 
more deeply forked. One sees immedi¬ 
ately that it is a freer, swifter swimmer, 
navigating wider stretches of more open 
water. 
WHY SWIFT SWIMMING FISH HAVE 
FORKED TAILS 
Most marine animals which swim, es¬ 
pecially swiftly and continuously, have 
a forked tail-fin. This shape of tail 
avoids the space immediately behind the 
axis of the body where the stream-lines 
following the sides (of a moving fish) 
converge. A rounded or pointed tail which 
would occupy such area would be a drag. 
Whales and Porpoises, though they 
move the tail up and down instead of 
from side to side, have a forked tail-fin, 
only it lies in a horizontal instead of a 
vertical plane. The wide ranging mem¬ 
bers of the mackerel family and other 
more or less related marine fishes have a 
forked tail-fin set on a firm, narrow base; 
and the freest swimming sharks (Mack¬ 
erel sharks and the Man-eater) have ac¬ 
quired a tail of the same shape, though 
the ordinary shark tail is weak and un- 
symmetrical. 
Fresh-water minnows almost invari¬ 
ably have a forked tail-fin, waters which 
they have to traverse being considerable 
in relation to the small size of the fishes 
themselves. 
In the blues and greens of the waters 
through which it swims, the Yellow Tail’s 
bright yellow tail probably makes a shin¬ 
ing mark, though its colors otherwise are 
well calculated to give it a low visibility. 
Are we to conclude from this that there 
are no larger fishes which prey on it? No; 
there pretty surely are such fishes, though 
it may well be so swift as to escape many. 
DEEP SWIMMING FISH ARE OFTEN RED 
IN COLOR 
As regards concealment, having a yel¬ 
low tail must be a disadvantage to it, 
and is a character which would doubtless 
have been lost in the keen competition of 
the tropical waters where it lives, were 
there not, on the other hand, some com¬ 
pensating advantage. It may be a badge 
of identification, useful to a school in 
keeping together. 
It has been previously mentioned that 
the Red Snapper comes from deeper 
water than other common snappers. 
There is a tendency for fishes which 
swim deep down under the blue or green 
sea and yet within the range of surface 
light penetration to be red in color. A 
great many are not, to be sure, but a 
larger proportion are red here than else¬ 
where, frequently a clear bright striking 
red all over. 
It seems almost a pity that the light 
in which they live is so green that the 
color, red, must appear an intangible 
neutral gray! Perhaps it gives them a 
useful inconspicuousness down there, or 
perhaps it absorbs a maximum amount 
of the dim, strongly blue-green sunlight, 
which is in some way beneficial. 
One of the commonest species of the 
surface reefs, the Squirrel Fish (Color 
Plate, page 175), has a regular, bright, 
*‘deep-water” red color. But the mystery 
of how it comes to such a color is easily 
explained, for it has similar relatives living 
deeper down. Evidently the Squirrel Fish 
has recently come up in the fish world, 
and its big eyes indicate, that it has 
not yet adjusted itself to the bright light 
of the surface sun, but is more or less 
nocturnal. 
The Gulf Stream runs so close to the 
coast of Florida that, when the wind is 
right, quantities of the drifting yellow 
gulf-weed it carries are washed ashore 
and into the bays. A variety of fishes 
hide in and about this weed. ■ 
One of the commonest and perhaps the 
most interesting, namely, the Mouse Fish, 
spends its entire life in the drifting sar- 
gassum. Colored in wonderful mimicry 
of this habitat, its shape also, grotesquely 
irregular, covered with leaf-like processes 
or flakes, heightens the resemblance, so 
as to make it well nigh invisible. This 
protection against larger fish which might 
disturb it probably also serves the pur- 
